Of the standard processes in forming a comestible, a critical feature is having the final product formed from a fluid having the right viscosity and density. In forming a fluid to make the desired product, it necessary at times to mix at least one liquid with at least one gas to form a final liquid. It is also necessary at times to mix at least two liquids of differing viscosities or densities. To either a liquid-gas mixture or a liquid-liquid mixture, it is desirable to add at least one solid such that the fluid to make the final product becomes a slurry.
These different combinations make a fluid or slurry having the right viscosity and density. It is very difficult to control each component to achieve this goal. Such a procedure requires a constant data feedback to provide for adjustments. The adjustments must be available quickly. This is especially true when one desires to have a continuous process.
Control of a gas addition to a fluid stream is required in several processes to create a final fluid characteristic, which is generally of lesser density than the original fluid stream. The actual control means for the gas stream can be accomplished by a variety of approaches. Control of a gas rate by an in-line orifice creating a critical velocity for the gas is known in the art, but does not make use of a primary fluid metering device.
Another method for gas incorporation has air being introduced into a fluid by the fluid flowing through and drawing air into a cylindrical bore at the same time. The air volume is dependent on the rate of the flowing liquid.
Also ambient air may be introduced through a variable opening into a flowing liquid stream. Again the gas addition is varied by outside intervention and is not controlled based upon the flow of the liquid.
Another method determines the relative air or gas content in a product by comparing the relative volumes in a sampling chamber by compressing the sample with a series of movable pistons. This method can be used as a means of measuring the relative volume differences in two sample mixtures of liquid and air, but does not control the rate of the gas addition nor does it operate as a control to continuously control the gas addition rate.
Still another method utilizes a volumetric electromagnetic flowmeter connected to a control circuit to control addition of air to a liquid utilizing air mass flow control. This approach is based upon a volumetric flow metering device and cannot compensate for variations in incoming fluid density by a volumetric metering means. The liquid/air ratio is controlled on a direct volume of liquid to volume of gas basis; and, therefore, will not yield a liquid of desired density, since temperature and mass of the liquid have not been measured.
A further method describes mixing a liquid component with another liquid component based upon a volume measurement from a measuring device. Although addition of one liquid to another may alter the density of the resulting mixture, no means for determining density is provided.
Also, a method allows for addition of a gas to a liquid stream based upon maintaining a gas to liquid ratio by means of pressurizing the gas/liquid mixture. The purpose of this method is to create a carbonated icy beverage which contains gas to an approximate volume. The density of the resulting liquid may vary and does not create a basis for determining the amount of gas which is incorporated into the beverage.
Still another method references introduction of air into a freezing chamber, while monitoring the loading of a dasher motor to maintain a constant desired product density. This continuous process alters the air intake by indirect measurement means and cannot quantify or control the liquid to a desired density setpoint except as determined by external sampling means to effect an alteration of the operating point.
Yet a further method determines the overrun of a frozen product by allowing a batch process to continue whipping air into a frozen product until a motor load setpoint is reached. As a batch process, this does not provide for continuous production of the frozen product and further does not attempt to measure the density of the final mixture.
Mixing of two or more fluid streams is referenced numerous times in prior art. However, nothing in the prior art involves a multiplicity of individual density controlled streams being utilized, so as to yield a final mixture of a desired density.
Other mixing methods for use in the chemical field are not adaptable to food processes. A known fuel dispensing system depends on mechanically interlocked proportioning valves for two streams only and does not measure the density of the resulting mixture. Further no overall flowrate control is included as the dispensing rate is dependent on the external fuel pumps and position of the manual dispensing nozzle. The volumetric flowmeters, which provide volume related information only, are not capable of determining the density of a fluid stream.
A resin foaming process also describes two liquid streams only with volumetric type flowmeters. Ratio control is by means of a servo motor driven needle valve based upon flowrate signals from the flowmeters. Overall flowrate control is manual via the nozzle and there is no requirement for density control of the final foam. The final foam quality is a result of chemical interaction between the resin and foaming agent.
Another resin foaming process references mixing of two streams comprised only of a resin and foaming agent. For similar reasons, this resin foaming application is not based upon density information and does utilize volumetric flowmeters.
The petroleum industry realizes a control of an air to liquified petroleum gas ratio to yield a mixture of comparable heating value equivalency to that of a third stream of natural gas. Although specific gravity of the streams is measured, it is with the purpose of determining the heating equivalency value of each gas stream, which is expressed in heat units per unit volume. The system does not make use of density as the controlled parameter of the final gas mixture. Rather it utilizes the control capability to mix gases to achieve a uniform heating value. Further, overall system flowrate is determined to be that of the rate of gas consumption by the downstream combustion process.
Another non-food application of a mixing apparatus makes specific use of volumetric metering means and does not attempt to determine the final density of a product. The reference to viscosity control is a result of mixing water with a polymer in a controlled ratio to yield a final mixture of desired viscosity without concern for final product density.
Yet another non-food industrial application combines streams of acids of differing specific gravities to yield an acid of a desired specific gravity. No attempt is known relative to controlling the overall system flowrate nor is a recipe followed to create a series of flow ratios for the various acid streams. Additionally there are no adequate devices to create and control the system to an overall flowrate or to generate data related to the totalization of final product mixed.
Still another non-food industrial application makes use of volumetric metering devices on water streams to produce a water/cement slurry of a desired density as monitored by a density meter based upon radiation transmittance through the slurry. Only two streams of water are utilized and the measurement means is not suitable for a food related application. Also a multiplicity of individually density adjusted process streams are not included so as to be combined by a recipe function to determine the mixing ratios.
In the processed food arts, combinations of components to form various foods are desired and even required. When the resulting food must have a desired density, adding streams to be mixed therein geometrically compounds the problem of achieving a certain density within a desired range. It is difficult to obtain a final product comprised of specific ratios of each stream as defined by a recipe structure and to control the possible addition of added ingredients on a mass basis to create a final mixture of a desired density, that is weight per unit volume.
In a multi-stream procedure, a change in recipe also creates major problems. It is desirable to change a recipe simply used in a process in order to switch to a desired food or flavor; and yet maintain a series of recipes with each recipe having information relative to the desired density, production temperature, pressure, and ratio of each process stream. In this fashion, a substantially similar process can be used to form foods having different physical characteristics. The multiple streams used to form the final food multiply the difficulty of such a system.
In such a process, it is desired to obtain constant feedback on process to make appropriate adjustments. Multiple streams and variable recipes complicate both obtaining and interpreting information on the process continuously. Even if such steps can be automated, it is still necessary to provide a means to manually intervene and override a specific controlled parameter on one or more process streams. This too is clearly difficult to accomplish in an efficient manner.
Even if such equipment is possible, it cost prohibitive to replace existing equipment. It is desirable to have the multi-stream equipment be compatible with a variety of preexisting process equipment and to allow for integration of new equipment therewith to update the production technology in a process facility.
Thus it may be seen that a multi-component food creates many manufacturing problems. A method and apparatus to overcome these problems are highly desirable.